Morteza Imani

Environmental Radioactivity Risk Mapping

Partnering with the Nuclear Science & Technology Research Institute (NSTRI) and collaborators, I helped measure, model, and map indoor radon/thoron exposure across urban areas, identify high-risk zones, and test mitigation via ventilation using CFD.

Collaboration: NSTRI Focus: Indoor Radon/Thoron, Risk, CFD Outputs: City heat maps, dose/risk, guidance

Executive summary

Iran has pockets of elevated natural background radiation and radon exhalation from soil/building materials. Our program measured indoor radon and thoron concentrations (multi-season), soil-gas radon, and indoor/outdoor gamma; produced city-scale indoor radon maps; and quantified annual effective doses, excess lifetime cancer risk, and expected lung-cancer cases per million. We also built CFD models to evaluate how natural ventilation, air-change rates, and room layout affect occupant exposure and to translate findings into building guidance (ventilation targets, critical zones, and material considerations).

  • Measured 222Rn/220Rn indoors over summer/winter using CR-39 (RADUET/NRPB) and active monitors.
  • Measured soil-gas 222Rn; linked geogenic signal with indoor levels.
  • Computed annual effective dose & risk metrics for residents and workers.
  • Mapped city exposure (1×1 km grid) with IDW/Kriging and cross-validated (MAE/RMSE).
  • Validated CFD room simulations (ANSYS Fluent) against active & passive measurements.
  • Delivered policy-ready heat maps and mitigation guidance for building codes and ventilation.

Measurement & modelling workflow

Field measurements

  • Indoor 222Rn/220Rn (two seasons, ground-floor living rooms, 78+ dwellings).
  • Soil-gas radon (CR-39 in PVC wells, low-moisture season), plus gamma dose surveys.
  • Personal radon dosimetry for occupational groups to estimate dose by job/hrs.

Risk & mapping

  • Annual effective dose and ELCR/LCC calculations (UNSCEAR/ICRP factors).
  • Indoor radon map (1×1 km cells) using IDW, OK, EBK — selected by MAE/RMSE.

CFD ventilation analysis

  • Finite-volume CFD (Fluent) with species transport for 222Rn and measured exhalation flux.
  • Scenarios: door open/closed; ACH 0.3–4.3 h−1; humidity sensitivity.
  • Validation with AlphaGUARD/RAD7 & CR-39; typical errors 2–11% at 1 ACH.
  • Design outputs: breathing-zone concentrations, hotspots near floor & low-velocity corners, ventilation set-points meeting reference levels.

Key outcomes

  • Seasonality confirmed: winter levels > summer; ventilation is decisive.
  • City heat map highlights central/southern districts as higher-risk cells in studied case.
  • Average residential annual dose dominated by radon/thoron fraction of indoor dose budget.
  • Workplace assessment: office staff may exceed miners due to poor ventilation & materials.
  • CFD pinpoints where to place inlets/outlets and what ACHs achieve target reference levels.
  • Evidence package informed draft guidance on ventilation and material choices.
Impact: Findings were used by the Nuclear Science & Technology Research Institute to support proposed building regulations aimed at radon mitigation (ventilation targets and material considerations).

Selected visuals

How this helps industry & cities

For regulators & planners

  • Prioritize inspections by heat-map risk rank.
  • Codify ventilation set-points (ACH) for reference levels.
  • Target materials testing in high-risk districts.

For building owners

  • Ventilation upgrades scoped by CFD hotspots.
  • Material selection guidance (NORMs awareness).
  • Simple monitoring plans with actionable thresholds.